Automobile windshield wipers generally comprise strip rubbers attached to a wiper blade, where the blade is attached to a wiper arm. As the wiper arm is translated by a drive apparatus, the strip rubbers slide over the vehicle's windshield to remove moisture (e.g., raindrops, snowflakes), dust, etc., thereby improving visibility. Because the region of a wiper blade which contacts the windshield is generally strip-shaped, wiper blade rubbers are often referred to as strip rubbers or wiper blade rubbers.
Wiper blade rubbers are commonly made of elastic materials, and can be divided into a head portion that is joined to the frame of a wiper blade, and a wedge-shaped portion that contacts the windshield. The wiper head and wedge-shaped portions are assembled in a way that allows them to bend or fold in a direction opposite to wiper movement, due to frictional forces between the windshield and the wiper rubbers. As a result, wiper rubbers can maintain a consistent, uniform cleaning ability, with minimal slippage.
Materials for preparing wiper blade rubbers preferably have not only good mechanical properties, but also satisfy additional requirements related to vehicle safety against external influences. Wiper blade rubber materials should be flexible and be able to slide smoothly over the windshield. Furthermore, blade rubber materials should have resistance to environmental influences, including, for example, oxidation (e.g., ozone cleavage), mineral oil, and chemicals contained, for example, in washing fluid.
Wiper blade rubbers are generally composed of rubbers, such as vulcanized natural rubbers or synthetic rubbers. However, in order to improve the sliding properties of the rubbers, additional treatments have been suggested, such as surface coatings, chlorination, and treatment with sliding powder agents such as molybdenum sulfide.
The wiper blade rubber described in DE-C-35 27 093 preponderantly consists of EPDM (Ethylene-Propylene-Dien-Monomer), which includes unsaturation sites outside the main ring of the polymer. As a result, the EPDM is not halogenated and has low resistance to mineral oil and chemicals contained in washing fluid. Therefore, according to DE-C-35 27 093, in order to improve the sliding properties and the endurance of wiper blades consisting preponderantly of EPDM, chlorinated diene-type rubber segments were placed on a matrix consisting of EPDM in regions that slide over the car windshield during proper use. However, wiper rubbers having such a complex structure, with layers of different rubber materials is disadvantageous.
WO 1999/39948 (Corresponding to Korean Laid-open publication No. 10-2001-0015914) discloses a wiper blade in which different kinds of rubber materials are used for the head and wedge portions of the wiper. The head portion is made of a diene-type rubber that can be halogenated, resulting in favorable sliding properties and smooth operating conditions. Further, the wipers also provide improved access to the connecting region in which the wiper blade cooperates with the supporting strip and the spring rail of the metallic support, as well as a harder surface. Chloroprene rubber (CR) is used for the flexing portion and the wedge portion of the wiper blade, and has excellent mechanical properties with high resistance to environmental conditions, including bad weather, aging, chemicals, and temperature. Therefore, improved wiper quality can be achieved in a simple and inexpensive manner according to said invention. However, chloroprene has certain limitations, including poor resistance to frictional forces which occur between windshield glass and wiper rubbers.
Korean Patent Reg. Publication No. 10-2005-0006677 discloses a windshield wiper blade coating composition and related coating methods. The coating composition comprises graphite and dimethyl silicone oil as essential ingredients, and further comprises a resin selected from polyol resin, urethane resin, fluoro resin having hydroxyl group, epoxy resin and silicone resin, and a solvent. When windshield wiper blades coated with such compositions are operated over a glass windshield, a water-repelling film having high durability is formed on the glass, which decreases operating noise and shaking movements. However, according to the disclosure of said patent, the compositions use an organic solvent selected from methylethyl ketone, toluene, xylene and butyl acetate, and the resins are not limited to water-based resins. Accordingly, the compositions invariably give rise to environmental pollution.
What is needed is a treatment for a wiper blade that provides improved performance and durability while minimizing environmental pollution. The invention is directed to these and other important needs.